A prospect for single molecule information processing devices

Due to the foreseen limitations of the present information technologies, such as semiconductor technology as well as magnetic disk technology, next generation technology is desperately needed. 'Single molecule devices' have been proposed as candidates to supersede the present devices for more than quarter of a century, but have not been made practical yet. The main reasons are that it is very difficult to make an access to a single molecule, and that the electron states of the molecule are very complicated when connected to the electrode. The progress in scanning probe microscope technologies and simulation technologies have made it almost possible to handle a single molecule and to foresee characteristics. The aim of this paper is to review a prospect for single molecule devices for the future information technologies, placing emphasis on the possible advanced switching devices. Four major milestones towards the final goal are proposed, and the current status of the first milestone is summarized, which includes theoretical treatment, molecular synthesis and measuring technology developments. New architectures might also be necessary which are suitable for molecular information processing systems.